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Thursday, 5 April 2012

Manchester United Get Their Just Deserts at Old Trafford.

The Patrick Vieira row over referees appearing to favour big,well resourced teams who originate from Manchester and are fighting for the Premiership title when deciding whether or not to award penalties continues to rumble on.We've shownhere that both sides from across the blue and red divide can benefit from the occasional lapse in refereeing concentration,but also that over the stretch the better teams do more attacking and therefore get the lion's share of the attacking spoils.For once Graham Poll also put one and one together and came to the same,almost certainly correct conclusion that better sides get more goals,more corners,more shots and more penalties.

To be fair to Vieira he did qualify his remarks by singling out Old Trafford as a venue where opponents find penalty decisions difficult to get,so instead of looking at both home and away matches,I've concentrated solely on home games.We saw previously that if Premiership sides scored say 60% of the goals that were registered in their matches,they could expect to gain a very similar proportion of the penalties awarded in those same games.And the following graph paints a very similar picture if we look at only a team's home games.

I've looked at the last six season including the present one and although the correlation isn't quite as tight because I've used slightly fewer teams and games,the previous trend is still present.The proportion of penalties you are awarded at home is intimately connected to the proportion of goals you score at home and for much of this sample it is a one to one relationship as before.If you get half your game's goals you should expect to get around half of the penalties that are awarded. Manchester United at Old Trafford scored 80% of the goals over the period I looked at and they received 73% of the penalties,sample size caveats apply,but you could decide that there's the possibility that they were actually short changed.Or maybe the referees invoked their own mercy rule in games where United were romping to victory.

A penalty that is given for a simple trip in the box with little immediate threat being exerted towards the goal is often difficult to take if your side is on the receiving end.But the decision is no different to the steady accumulation of free kicks that happen as a superior side launches wave upon wave of attacks and no side at present is superior to the likes of Manchester United and City,especially on their own turf.So it is very likely the bulk of the penalties will go to these sides when they play at home.Some visitors to Old Trafford even manage to concede two penalties in 15 minutes,Stoke for example back in January.

Vieira's complaint arose from a penalty that wasn't given,but the relationship that exists between United's goal scoring ability and their penalty acquiring talent obviously also applies in reverse to United's defence.They allowed only 20% of all the total goals scored in matches at home and so they would expect to concede about 20% of the spot kicks that were awarded.So the award of a spot kick to United's visitors should be a relatively rare event,four United penalties to every one for the visitors and it's scarcity shouldn't be a sign of anything sinister.No doubt Fulham were disgruntled because of the spot kick they didn't get on Monday.But basing a conspiracy theory on an isolated incident at the tail end of a season ignores the bigger picture.One contentious decision is simply an anecdote.

Vieira goes on to say that the same bias occurs in both Spain and Italy,but again the figures say not.As the following two graphs illustrate the same type of relationship between attacking endeavour and reward exists in both Serie A and La Liga.

These graphs don't differentiate between venue,but are identical in form to the plot for the EPL indicating that it is very likely that attacking intent on the continent reaps a long term penalty kick reward and miserly defences largely avoid conceding spot kicks.